An accurate method to measure beam current (BC) and beam diameter (BD) of an electron beam lithography by using a Faraday cup and a sharp edge is described. The sharp edge specimen was fabricated by an isotropic process in < 100 > silicon wafer which yielded a high etch rate ratio and gave exceptionally smooth etched faces. The saw-tooth of the edge was less than 30 nm. Detailed investigations about the measured BS and BD at various conditions showed that BC and the square of BD were linear with an offset, which was the sum of optical aberrations, noise, and edge width.